The widespread use of oils, fats and waxes in industrial operations, as in motor vehicle technology, in the material-removing treatment of metals in chemical factories, refineries, and the like would lead to considerable environmental damage if the oil-emulsified waste waters were not pre-treated to remove a substantial percentage of oil contaminants contained therein.
Numerous procedures have been devised for eliminating harmful substances from waste waters. One such procedure chemically reacts the oily water in monophase or polyphase systems, for example, by combustion or biological degrading (decomposition). This process, however, requires complex reaction installations resulting in considerable expenditures. Furthermore, such methods include gaseous combustion by-products which, themselves, must be eliminated in order to avoid environmental damage.
Another known practice evaporates the water from an oily water emulsion, leaving the substances contained therein in concentrated form, whereby the concentrate may subsequently be deposited or burned in suitable places. The evaporation of the waste waters, however, requires a large amount of energy and is, therefore, not economically practical.
A further method of waste water treatment separates emulsified oils, fats or other floating substances in the waste water by chemically, thermally, electrically or mechanically decomposing the emulsion and absorbing the precipitated substances. Yet another process separates out extremely fine dirt particles from the waste water by chemical flocculation and binds the separated dirt particles to a calcium hydrate compound. This process is carried out using iron-II salts, aluminum sulfate, calcium hydrate, and lime or sodium aluminate in conjunction with activated silicic acid.
The most usual method of treatment splits and emulsion by adding an electrolyte. The electrolyte serves to precipitate the oil, fat or other floating particles, for sedimentation and/or absorption.
These known processes, however, have inherent weaknesses and are not adaptable to all situations. Frequently, the waste water has to be recirculated several times in order to obtain an extensive separation of the oil, fat or other contaminants. Also, problems often arise in the adsorptive purification of the waste water because of the limited chargeability of the adsorption agent or because of the deficient bonding of the oily substance to the adsorbing agent, whereby the oily contaminant is again liberated by environmental influences and its harmful effects develop anew.